This invention concerns a character synthesizer for inserting character signals into video signals, and more particularly, a system for causing the characters to automatically have the complementary colors of the background video signals.
Conventionally, the character synthesizer can insert desired characters into desired positions of the video signals. It is widely used in video cameras having character generators, and video cassette recorders making it possible to insert characters into the screen during video editing, and also broadcasting. Such a conventional character synthesizer uses only monochromatic colors, for example, red, blue, green, or white, regardless of the colors of video signals, so that it is difficult or impossible to perceive the characters inserted into the image displayed on the screen if the color and the brightness of the video signal are the same as those of the character signal.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a character synthesizer wherein the color of the characters inserted into the image displayed on the screen always has the complementary relationship with that of the image by detecting the color and the brightness of the video signal.
It is another object of the present invention to provide a color component separating means for separating the color signal components according to the level of the color-phase detected by decoding the video signal to be displayed on the screen.
It is still another object of the present invention to provide a complementary color circuit for generating the signal complementary with the color of the video signal by encoding the color signal separated according to the level of the detected color-phase.
According to the present invention, a character synthesizer for inserting into video signals characters having the complementary colors with the video signals includes:
a video decoder for decoding the incoming video color signals to produce color-difference signals;
a color-phase detector for detecting the color-phase voltage of the color-difference signals and separately producing the color signals and the brightness signals;
an excessive white detector for comparing said brightness signals with a reference voltage to produce an excessive white signal when said brightness signals are excessively white;
a low saturation detector for comparing said color signals with the low saturation voltage to produce the low saturation signal when said color signals are in low saturation;
a character generator for generating character signals;
a complementary color detecting and control device for comparing the color-phase voltages of the video color signals with a plurality of reference color voltages of given colors to separate the components of the video color signals so as to obtain the colors complementary to the video color signals, the complementary colors being used to generate the color signals of the characters, the color signals being transformed according to the excessive white signal and the low saturation signal;
a video encoder for encoding the color signals of the characters;
a mixer for combining the incoming video signals and the video-encoded color signals of characters to output the character-combined video signals; and
a delay device for delaying the character signals by the amount of time for complementary color transformation and encoding, and to generate a character synthesizing control signal to the mixer.